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An allergy is an adverse reaction by the body’s immune system to contact with a substance that is harmless for most people.
All of us are exposed to different potential allergens throughout the day. Where the sufferer is and the time of day when symptoms occur can give clues about the cause of the allergy. For example, if symptoms appear when a patient is outdoors, then pollen is a likely trigger. Symptoms lasting throughout the spring and summer are likely to indicate an allergy to more than one type of pollen.
Causes
Pollen
If a sufferer presents airborne allergy symptoms at about the same time each year, then this would indicate sensitivity to pollen or mould spores. The time of year should give a good indication as to which pollens are responsible. The length and severity of the pollen season varies from year to year depending on the weather.
Mould spores
About 20 per cent of people who suffer from airborne allergies are affected by mould spores. Moulds prefer damp conditions – the kitchen and bathroom, in wooden window frames, the soil of houseplants and under wallpaper. Outside, there are plenty of moulds in the soil, in rotting wood and leaves, grass cuttings and compost heaps, so digging the garden or potting plants can bring on symptoms.
House dust mites
House dust mite droppings are the most common trigger of airborne allergy. House dust mites are almost always present, even in the most clean and tidy homes. In some ways they serve a useful purpose in disposing of shed skin flakes. Mostly they like damp and dusty places.
Pets (dander)
Dander, the mixture of small particles of fur, skin scales and saliva of pets, is responsible for the allergy, rather than just the fur itself. Cats, in particular, cause allergies but dogs and rabbits can also trigger the itching and sneezing of airborne allergy. Because cats groom themselves so thoroughly, the saliva finds it way on to carpets, furniture and other surfaces.
Other triggers
In addition to these common allergy triggers, there are other triggers that can make life difficult for airborne allergy sufferers, even though they may not be allergens themselves.
Air pollution
High concentrations of nitrogen dioxide, sulphur dioxide and other chemicals in the atmosphere can irritate the nose and airways even in those who do not suffer from airborne allergy.
Air-conditioning
Air-conditioning that draws chemicals, dust and pollution from outside, can make allergic reactions worse. Changes in temperature, low humidity and other factors can increase nasal sensitivity. Even good air-conditioning, with efficient air filters that can reduce pollen levels, will not get rid of all air pollution.
Symptoms
The symptoms of an airborne allergy, while similar to other conditions affecting the nose and eyes, are quite distinctive:
- Itchy nose (palate/throat may also be itchy);
- Blocked nose (often associated with congested sinuses);
- Itchy eyes;
- Watery eyes;
- Pressure around the eyes and sinuses;
- General tiredness, inability to concentrate, headache, malaise.
Treatments
There are several OTC treatment options for use in airborne allergy. Pharmacists should ask customers which symptoms are the most troublesome and recommend treatments accordingly.
Antihistamines
Antihistamines work best to control symptoms that are a direct result of histamine release – sneezing, runny and itchy nose. Other aspects of the allergic reaction are not directly related to histamine, so antihistamines are less effective than some other treatments (such as nasal corticosteroids) in controlling nasal congestion and the blocked-up, groggy feeling.
Oral antihistamines
Some older types of oral antihistamines, such as chlorphenamine, have sedative properties and are therefore likely to cause drowsiness as a side-effect because they block the actions of histamine in the brain. However, this can be an advantage if the allergy is disturbing sleep.
Newer antihistamines, such as cetirizine, acrivastine and loratadine, do not penetrate the brain, so are classed as ‘non-sedating’ and are unlikely to cause drowsiness or other central side-effects. Acrivastine has a rapid onset but needs more frequent dosing than the longer-acting cetirizine and loratadine. Individual response to antihistamines varies widely and choice is often based on personal preference.
Topical antihistamines
These are available as nasal sprays (e.g. azelastine, levocabastine) and provide local relief from nasal itching, sneezing and runny nose. Topical antihistamines are also available as eye drops (e.g. antazoline, levocabastine) for treatment of allergic eye symptoms.
Decongestants
Decongestants are available OTC as oral or topical preparations (e.g. pseudoephedrine). They constrict swollen blood vessels in the nose and help reduce nasal blockage. They have no effect on mediators or cells involved in the allergic reaction, so have no effect on symptoms such as sneezing and runny nose. However, they are often used in airborne allergy treatment in combination with antihistamines to provide added relief from nasal congestion (a symptom not relieved by antihistamines). Topical decongestants should not be used for more than seven consecutive days.
Mast cell stabilisers
These are available as topical preparations (e.g. sodium cromoglicate) to treat airborne allergies and eye symptoms. It is not yet clear exactly how these agents work, but they seem to make mast cells less likely to release inflammatory mediators on exposure to allergens. Mast cell stabilisers can prevent an allergy from developing as well as treating symptoms, but they must be used regularly and frequently (usually up to four times daily).
Nasal corticosteroids
Nasal sprays (e.g. beclometasone dipropionate, fluticasone propionate) are available OTC for the prevention and treatment of airborne allergy. They reduce all nasal allergy symptoms, including sneezing, runny or itchy nose, itchy or watery eyes and congested nasal or sinus passages. Their anti-inflammatory action damps down the allergic response in nasal membranes. Nasal corticosteroids should be used regularly for best effect but must not be used continuously OTC for more than three months without medical advice. They may not be appropriate to treat airborne allergy in asthma sufferers who may already be receiving anti-asthma corticosteroid therapy. In this case, medical advice should be sought.
Desensitising injections
This treatment is usually for the most severe cases when recommended by a GP.
Differential diagnosis
Some other conditions can have symptoms similar to airborne allergy. It is important to be aware of these so that the appropriate advice is given. The following diagnoses may have symptoms in common with airborne allergy, but can be distinguished as follows:
- The common cold (acute infectious rhinitis): Viral infection with gradual onset, maybe a raised temperature, symptoms usually last about 4–7 days, nasal itching and eye symptoms are uncommon;
- Sinusitis (chronic infectious rhinosinusitis): Symptoms include purulent nasal discharge, facial pain and pressure, post-nasal drip often with cough;
- Rhinitis due to an obstruction e.g. presence of a foreign body, deviated nasal septum, nasal polyps, nasal tumour. In contrast to airborne allergy, symptoms are usually unilateral (in one nostril only).
Referral to a GP should be considered where symptoms are:
- Troublesome, severe, long-term persistent;
- Suggestive of infection e.g. purulent discharge (thick green/yellow mucus), painful sore throat, earache/pain, facial pain/pressure, muscle pains, weakness, fever;
- Suggestive of non-allergic cause e.g. unilateral nasal symptoms, nasal blockage without other symptoms, loss of smell, post-nasal drip, recurrent nose bleeds, associated nasal/ear pain;
- Suggestive of undiagnosed or uncontrolled asthma e.g. accompanied by coughing, wheezing and/or shortness of breath;
- Unresponsive to OTC treatment within two to four weeks, or if troublesome side-effects occur.
Pregnant or breast-feeding women and children under the age of 12 should also be referred for medical advice.
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